The aims of this project are to determine the primary biosynthetic pathway(s), intracellular transport systems (e.g., cytosolic protein carriers versus Golgi apparatus), storage events associated with lamellar bodies, the mechanism of secretion at the cell surface, and the regulation of pulmonary surfactants in alveolar type II cells. Unlike many investigations in this field in which results have been based on heterogeneous lung cell preparations and lavage, our studies are being done with a homogeneous population of alveolar type II cells from adenomas induced by urethan injections; in some experiments these type II cells will be grown as monolayer cultures for investigating the regulation and mechanism of surfactant secretion. Current studies of membrane topography in the adenoma type II cells are focused on whether there is an asymmetric distribution of pulmonary surfactants and the enzymes responsible for their synthesis in microsomal vesicles. To better understand the deacylation-reacylation reaction that forms surfactant lipids, attempts will be made to isolate subsets of phospholipase A2 from adenoma type II cells by affinity chromatography so that specificity of the specific A2 enzymes can be determined with various acyl substituents at the sn-2 position of the phosphatidylcholine substrates. Studies will also be initiated to determine which enzymes of the biosynthetic pathways for pulmonary surfactant are the rate-limiting steps under conditions that alter surfactant synthesis in lung disease, e.g., when surfactant accumulates after NO2 exposure.